1. Field of the Invention
The present invention relates to a plasma display apparatus, and more particularly, to a plasma display apparatus and a method of driving a plasma display apparatus including address electrodes (X) and scan electrodes (Y).
2. Description of the Background Art
In general, a plasma display panel excites phosphor due to 147 nm ultraviolet rays generated when an inert gas such as a combination of helium and xenon (He+Xe) or neon and xenon (Ne+Xe) is discharged, thereby displaying an image including characters or graphics.
FIG. 1 is a perspective view illustrating a structure of a general plasma display panel.
As shown in FIG. 1, the plasma display panel comprises a scan electrode 12A (Y) and a sustain electrode 12B (Z) formed on an upper substrate 10, and an address electrode 20 (X) formed on a lower substrate 18.
The scan electrode 12A (Y) and the sustain electrode 12B (Z) include a transparent electrode and a bus electrode, respectively. The transparent electrode is made of Indium-Tin-Oxide (ITO). The bus electrode is made of metal for reducing resistance.
An upper dielectric layer 14 and a protection layer 16 are sequentially laminated on the top of the upper substrate 10 on which the scan electrode 12A and the sustain electrode 12B are formed.
Wall charge is charged on the upper dielectric layer 14, the wall charge being generated when plasma is discharged. The protection layer 16 prevents the upper dielectric layer 14 from damaging due to sputtering generated when plasma is discharged and enhances efficiency of second electron emission at the same time. The protection layer 16 is usually made of magnesium oxide (MgO).
Meanwhile, the lower dielectric layer 22 and a barrier rib 24 are sequentially formed on the top of the lower substrate 18 on which the address electrode 20 (X) is formed. A phosphor layer 26 is coated on the surface of the lower dielectric layer 22 and the barrier rib 24.
The address electrode 20 is formed in the direction to cross the scan electrode 12A and the sustain electrode 12B. The barrier rib 24 is formed parallel with the address electrode 20 to prevent ultraviolet rays and visible rays generated by discharge from being leaked to adjacent discharge cells.
The phosphor layer 26 is excited due to ultraviolet rays generated when plasma is discharged to generate any one visible ray of red, green and blue. An inert gas for discharge such as a combination of helium and xenon (He+Xe) or neon and xenon (Ne+Xe) is injected in discharge space of a discharge cell formed between the upper/lower substrate 10 or 18 and the barrier rib 24.
Predetermined driving apparatus are combined in a plasma display panel with such a construction so that a plasma display apparatus is formed.
FIG. 2 is a schematic circuit diagram illustrating a driving apparatus of a general plasma display panel.
Referring to FIG. 2, if a channel corresponding to a first scan electrode (Y1) is selected in a scanning process, channels corresponding to the rest of the scan electrodes (Y2, Y3, . . . , Yn) are not selected.
If a channel is selected in such a manner, a second switching element 213-1 of a first scan driver 210-1 corresponding to the selected channel and a switching element 220 for scanning are turned on.
At the same time, a first switching elements 211-2 to 211-n of scan drivers 210-2 to 210-n corresponding to the channels which are not selected and a switching element 230 for grounding are turned on.
If the switching elements operate in such a manner and a data voltage (+Vd or 0V) is applied to address electrodes (X1 to Xm) due to operations of first data switching elements 310-1 to 310-m or second data switching elements 320-1 to 320-m of a data driver IC 300. Therefore, write operations are performed within cells located on a first line.
Further, a data pulse is grounded via the first switching elements 211-2 to 211-n of the scan drivers 210-2 to 210-n corresponding to the rest of the scan electrodes (Y2 to Yn) and the switching element 230 for grounding.
If such a process is performed on all the scan electrodes, a scanning process is finished.
After the scanning process, a first switching element 240 for sustaining, second switching elements 213-2 to 213-n of the scan drivers 210-1 to 210-n and a switching element 260 for grounding are turned on.
Accordingly, a first sustain voltage (+Vsy), the first switching element 240 for sustaining, the second switching elements 213-2 to 213-n of the scan drivers 210-1 to 210-n, each of the scan electrodes (Y1 to Yn), the sustain electrodes (Z1 to Zn) and the switching element 260 for grounding make a loop so that the sustain voltage (+Vsy) is applied to the scan electrodes (Y1 to Yn).
Next, a second switching element 250, the first switching elements 211-2 to 211-n of the scan drivers 210-1 to 210-n and the switching element 230 for grounding are turned on.
Accordingly, a second sustain voltage (+Vsz), the sustain electrodes (Z1 to Zn), the scan electrodes (Y1 to Yn), the first switching elements 211-2 to 211-n of the scan drivers 210-1 to 210-n and the switching element 230 for grounding make a loop so that the sustain voltage (+Vsz) is applied to the sustain electrodes (Z1 to Zn).
Such a driving apparatus of the plasma display panel applies a scan voltage (−Vyscan) and a data voltage (+Vd or 0V) to corresponding electrodes through switching operations of switching elements included in the scan drivers 210-1 to 210-n and data driver ICs 300-1 to 300-m in the scan period, and a displacement current (Id) flows in the data driver ICs 300-1 to 300-m through the address electrodes in this process.
Since a general plasma display panel has a three-electrode structure, a first equivalent capacitor (Cm1) exists between two data electrodes adjacent to each other, and a second equivalent capacitor (Cm2) exists between a data electrode and a scan electrode, or a address electrode and a sustain electrode as shown in FIG. 2
Thus, since the state of a voltage applied to the electrodes varies depending on the operations of the switching elements included in the scan drivers 210-1 to 210-n and the data driver ICs 300-1 to 300-m in a scanning process, the displacement current (Id) generated due to the first equivalent capacitor (Cm1) and the second equivalent capacitor (Cm2) flows in the data driver ICs 300-1 to 300-m) through the address electrodes (X).
The magnitude of a displacement current flowing in such data driver ICs 300-1 to 300-m can be expressed in equation 1 as follows:id=C×(dv/dt)×f  EQUATION 1
“id” means the magnitude of a displacement current flowing through a data electrode, “C” means a capacitance between two data electrodes adjacent to each other, a data electrode and a scan electrode, or a data electrode and a sustain electrode, “dv/dt” means the variation of a voltage per time in a data electrode, and “f” means the number of voltage variance times of a data electrode.
FIG. 3 is a waveform diagram illustrating a data and a scan pulses applied to address and scan electrodes in a conventional scanning process.
As shown in FIG. 3, in the scanning process of a plasma display panel, a scan pulse is applied to each of the scan electrodes and a corresponding data pulse is simultaneously applied to the whole address electrodes. Accordingly, address discharge is generated due to a voltage difference between the scan pulse applied to the scan electrodes and the data pulse applied to the address electrodes.
Meanwhile, falling intervals (Tf1, Tf2) of such conventional data and scan pulses are synchronized so that they have the same falling time.
Thus, the falling interval (Tf1) of the data pulse becomes the same as the falling interval (Tf2) of the scan pulse so that electric potential of the data pulse varies rapidly in the falling interval (Tf1).
As described above, since the electric potential of the data pulse varies rapidly in the falling interval (Tf1), dv/dt in the equation 1 becomes large so that the peak of a displacement current becomes large, thereby deteriorating an EMI (ElectroMagnetic Interference) property. Therefore, there is a serious effect on a driving apparatus of a plasma display panel.